在做测试的时候，有时候需要不断的运行一个命令或者脚本，下面的这个脚本可以实现这个目的。

使用方法：

usage: period.sh [options] <cmd> <args>
    run command periodically.
options:
    -c <count> : how many times.
    -i <interval>: every <interval> seconds.
    -h: show help

示例：

   $ ./period.sh ls -l

   $ ./period.sh -i 3 ls -l

#!/bin/sh
PROG_NAME=period.sh
INTERVAL=1
ALWAYS_LOOP=1
COUNT=-1

#------------------------- functions --------------------------------------------------
usage() {
  cat << END
usage: $PROG_NAME [options] <cmd> <args>
    run command periodically.
options:
    -c <count> : how many times.
    -i <interval>: every <interval> seconds.
    -h: show help

END
}

run_cmd()
{
  echo $ $*
  eval $*
  echo
}

#---------------------------- main() --------------------------------------------------
# get command line arguments
while getopts "c:i:h" options; do
  case "$options" in
    c) COUNT=$OPTARG ;;
    i) INTERVAL=$OPTARG ;;
    h) usage; exit 0;;
    \?) usage; exit -1;;
  esac
done

shift $((OPTIND - 1))

if [ $# -lt 1 ]; then
  usage;
  exit 0;
fi

if [ $COUNT -ge 0 ]; then
   ALWAYS_LOOP=0
else
   COUNT=1
fi

while [ $ALWAYS_LOOP -eq 1 ] || [ $COUNT -gt 0 ]; do
  echo "#$INDEX Date: `date +%Y-%m-%d_%H:%M:%S`"
  run_cmd $*
  INDEX=$((INDEX + 1))
  COUNT=$((COUNT - 1))
  sleep $INTERVAL
done